CVE-2026-4137: Mlflow MLFlow Creates A Temporary File Vulnerability

HIGH
Advisory Identifier: GHSA-f2m9-wcf4-cwwx
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CVSS 7.0
CWE-378
Published
Advisory Summary

CVE-2026-4137 is a HIGH (CVSS 7.0) mlflow creates a temporary file vulnerability (CWE-378: Creation of Temporary File With Insecure Permissions) affecting Mlflow libraries in the PyPI ecosystem. The issue involves mlflow creates a temporary file with insecure permissions. Remediation is available by upgrading affected packages to version 3.11.0.

CVE-2026-4137 at a Glance

CVE Identifier CVE-2026-4137
GHSA Identifier GHSA-f2m9-wcf4-cwwx
Severity HIGH
CVSS v3.1 Base Score 7.0
CWE Classification CWE-378: Creation of Temporary File With Insecure Permissions
Affected Product Mlflow
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.0

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Local (AV:L)
Attack Complexity High (AC:H)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-4137

To remediate this vulnerability, upgrade all affected Mlflow dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

mlflow fixed: 3.11.0 
pip install mlflow>=3.11.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show mlflow

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-4137, inspect your installed packages using pip:

pip show mlflow

Analyze the terminal output to locate any version of Mlflow in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.11.0), your application is affected.

Note: The pip show mlflow command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-378: Creation of Temporary File With Insecure Permissions, where opening temporary files without appropriate measures or controls can leave the file, its contents and any function that it impacts vulnerable to attack. In Mlflow, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

In mlflow/mlflow versions prior to 3.11.0, the `get_or_create_nfs_tmp_dir()` function in `mlflow/utils/file_utils.py` creates temporary directories with world-writable permissions (0o777), and the `_create_model_downloading_tmp_dir()` function in `mlflow/pyfunc/__init__.py` creates directories with group-writable permissions (0o770). These insecure permissions allow local attackers to tamper with model artifacts, such as cloudpickle-serialized Python objects, and achieve arbitrary code execution when the tampered artifacts are deserialized via `cloudpickle.load()`. This vulnerability is particularly critical in environments with shared NFS mounts, such as Databricks, where NFS is enabled by default. The issue is a continuation of the vulnerability class addressed in CVE-2025-10279, which was only partially fixed.

CVE-2026-4137 Affected Mlflow Versions

1 component(s)
Fixed Versions:
3.11.0
Product / Package Ecosystem Affected Versions Fixed Version
mlflow
pypi/mlflow
PyPI
≥ 1.26.0
< 3.11.0
3.11.0

References

NVD — CVE-2026-4137 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-4137
Security Fix Commit FIX COMMIT
https://github.com/mlflow/mlflow/commit/1dcbb0c2fbd1f446c328830e601ca13a28219b8a
Security Fix Commit FIX COMMIT
https://github.com/mlflow/mlflow/commit/bd8854fb2b4b168a4384ebddc6c4a0b5d56aff01
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-4x5p-f36r-mxxr
Mlflow Source Repository REPOSITORY
https://github.com/mlflow/mlflow
Mlflow Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/mlflow/PYSEC-2026-2655.yaml
huntr.com/bounties/648dc30b-7... WEB
https://huntr.com/bounties/648dc30b-76c7-4433-86b8-f43d926fd8d6

Frequently Asked Questions

What is CVE-2026-4137?
CVE-2026-4137 is a security vulnerability in Mlflow involving MLFlow Creates a Temporary File With Insecure Permissions under CWE-378: Creation of Temporary File With Insecure Permissions.
Which Mlflow versions are affected?
Affected versions include releases prior to 3.11.0 across affected packages: mlflow.
What version fixes CVE-2026-4137?
Upgrading to 3.11.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is mlflow affected?
Yes, mlflow is affected in releases prior to 3.11.0. Upgrade your dependency to 3.11.0 or later.
What is the CVSS score of CVE-2026-4137?
CVE-2026-4137 has a CVSS v3.1 base score of 7.0 (HIGH) with vector string CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-4137?
CVE-2026-4137 is classified under CWE-378: Creation of Temporary File With Insecure Permissions (Opening temporary files without appropriate measures or controls can leave the file, its contents and any function that it impacts vulnerable to attack.).
How can I check PyPI dependencies for CVE-2026-4137?
Run the dependency tree command: 'pip show mlflow'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-f2m9-wcf4-cwwx",
  "modified" : "2026-09-01T01:05:34Z",
  "published" : "2026-05-18T21:31:53Z",
  "aliases" : [ "CVE-2026-4137" ],
  "summary" : "MLFlow Creates a Temporary File With Insecure Permissions ",
  "details" : "In mlflow/mlflow versions prior to 3.11.0, the `get_or_create_nfs_tmp_dir()` function in `mlflow/utils/file_utils.py` creates temporary directories with world-writable permissions (0o777), and the `_create_model_downloading_tmp_dir()` function in `mlflow/pyfunc/__init__.py` creates directories with group-writable permissions (0o770). These insecure permissions allow local attackers to tamper with model artifacts, such as cloudpickle-serialized Python objects, and achieve arbitrary code execution when the tampered artifacts are deserialized via `cloudpickle.load()`. This vulnerability is particularly critical in environments with shared NFS mounts, such as Databricks, where NFS is enabled by default. The issue is a continuation of the vulnerability class addressed in CVE-2025-10279, which was only partially fixed.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "mlflow"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.26.0"
      }, {
        "fixed" : "3.11.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-4137"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mlflow/mlflow/commit/1dcbb0c2fbd1f446c328830e601ca13a28219b8a"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mlflow/mlflow/commit/bd8854fb2b4b168a4384ebddc6c4a0b5d56aff01"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-4x5p-f36r-mxxr"
  }, {
    "type" : "PACKAGE",
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  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/mlflow/PYSEC-2026-2655.yaml"
  }, {
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    "url" : "https://huntr.com/bounties/648dc30b-76c7-4433-86b8-f43d926fd8d6"
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  "database_specific" : {
    "cwe_ids" : [ "CWE-378" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-29T19:53:36Z",
    "nvd_published_at" : "2026-05-18T21:16:40Z"
  }
}